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Enhance needless_borrow to consider trait implementations

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This commit is contained in:
Samuel E. Moelius III 2022-07-08 05:29:10 -04:00
parent 048e4d004a
commit a05cb74d30
7 changed files with 559 additions and 53 deletions
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289
clippy_lints/src/dereference.rs
View File

@ -1,24 +1,31 @@
use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_hir_and_then};
use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
use clippy_utils::sugg::has_enclosing_paren;
use clippy_utils::ty::{expr_sig, peel_mid_ty_refs, ty_sig, variant_of_res};
use clippy_utils::{get_parent_expr, is_lint_allowed, path_to_local, walk_to_expr_usage};
use clippy_utils::ty::{contains_ty, expr_sig, is_copy, peel_mid_ty_refs, ty_sig, variant_of_res};
use clippy_utils::{fn_def_id, get_parent_expr, is_lint_allowed, meets_msrv, msrvs, path_to_local, walk_to_expr_usage};
use rustc_ast::util::parser::{PREC_POSTFIX, PREC_PREFIX};
use rustc_data_structures::fx::FxIndexMap;
use rustc_errors::Applicability;
use rustc_hir::intravisit::{walk_ty, Visitor};
use rustc_hir::{
self as hir, BindingAnnotation, Body, BodyId, BorrowKind, Closure, Expr, ExprKind, FnRetTy, GenericArg, HirId,
ImplItem, ImplItemKind, Item, ItemKind, Local, MatchSource, Mutability, Node, Pat, PatKind, Path, QPath, TraitItem,
TraitItemKind, TyKind, UnOp,
self as hir, def_id::DefId, BindingAnnotation, Body, BodyId, BorrowKind, Closure, Expr, ExprKind, FnRetTy,
GenericArg, HirId, ImplItem, ImplItemKind, Item, ItemKind, Local, MatchSource, Mutability, Node, Pat, PatKind,
Path, QPath, TraitItem, TraitItemKind, TyKind, UnOp,
};
use rustc_index::bit_set::BitSet;
use rustc_infer::infer::TyCtxtInferExt;
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
use rustc_middle::ty::{self, Binder, BoundVariableKind, List, Ty, TyCtxt, TypeVisitable, TypeckResults};
use rustc_middle::ty::{
self, subst::Subst, Binder, BoundVariableKind, EarlyBinder, FnSig, GenericArgKind, List, ParamTy, PredicateKind,
ProjectionPredicate, Ty, TyCtxt, TypeVisitable, TypeckResults,
};
use rustc_semver::RustcVersion;
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::{symbol::sym, Span, Symbol, DUMMY_SP};
use rustc_trait_selection::infer::InferCtxtExt;
use rustc_trait_selection::infer::InferCtxtExt as _;
use rustc_trait_selection::traits::{query::evaluate_obligation::InferCtxtExt as _, Obligation, ObligationCause};
use std::collections::VecDeque;
declare_clippy_lint! {
/// ### What it does
@ -151,6 +158,7 @@ pub struct Dereferencing {
/// been finished. Note we can't lint at the end of every body as they can be nested within each
/// other.
current_body: Option<BodyId>,
/// The list of locals currently being checked by the lint.
/// If the value is `None`, then the binding has been seen as a ref pattern, but is not linted.
/// This is needed for or patterns where one of the branches can be linted, but another can not
@ -158,6 +166,19 @@ pub struct Dereferencing {
///
/// e.g. `m!(x) | Foo::Bar(ref x)`
ref_locals: FxIndexMap<HirId, Option<RefPat>>,
// `IntoIterator` for arrays requires Rust 1.53.
msrv: Option<RustcVersion>,
}
impl Dereferencing {
#[must_use]
pub fn new(msrv: Option<RustcVersion>) -> Self {
Self {
msrv,
..Dereferencing::default()
}
}
}
struct StateData {
@ -170,6 +191,7 @@ struct StateData {
struct DerefedBorrow {
count: usize,
msg: &'static str,
snip_expr: Option<HirId>,
}
enum State {
@ -250,7 +272,7 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
match (self.state.take(), kind) {
(None, kind) => {
let expr_ty = typeck.expr_ty(expr);
let (position, adjustments) = walk_parents(cx, expr);
let (position, adjustments) = walk_parents(cx, expr, self.msrv);
match kind {
RefOp::Deref => {
@ -331,20 +353,23 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
let deref_msg =
"this expression creates a reference which is immediately dereferenced by the compiler";
let borrow_msg = "this expression borrows a value the compiler would automatically borrow";
let impl_msg = "the borrowed expression implements the required traits";
let (required_refs, msg) = if position.can_auto_borrow() {
(1, if deref_count == 1 { borrow_msg } else { deref_msg })
let (required_refs, msg, snip_expr) = if position.can_auto_borrow() {
(1, if deref_count == 1 { borrow_msg } else { deref_msg }, None)
} else if let Position::ImplArg(hir_id) = position {
(0, impl_msg, Some(hir_id))
} else if let Some(&Adjust::Borrow(AutoBorrow::Ref(_, mutability))) =
next_adjust.map(|a| &a.kind)
{
if matches!(mutability, AutoBorrowMutability::Mut { .. }) && !position.is_reborrow_stable()
{
(3, deref_msg)
(3, deref_msg, None)
} else {
(2, deref_msg)
(2, deref_msg, None)
}
} else {
(2, deref_msg)
(2, deref_msg, None)
};
if deref_count >= required_refs {
@ -354,6 +379,7 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
// can't be removed without breaking the code. See earlier comment.
count: deref_count - required_refs,
msg,
snip_expr,
}),
StateData { span: expr.span, hir_id: expr.hir_id, position },
));
@ -510,7 +536,7 @@ fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) {
spans: vec![pat.span],
app,
replacements: vec![(pat.span, snip.into())],
hir_id: pat.hir_id
hir_id: pat.hir_id,
}),
);
}
@ -542,6 +568,8 @@ fn check_body_post(&mut self, cx: &LateContext<'tcx>, body: &'tcx Body<'_>) {
self.current_body = None;
}
}
extract_msrv_attr!(LateContext);
}
fn try_parse_ref_op<'tcx>(
@ -594,6 +622,7 @@ enum Position {
/// The method is defined on a reference type. e.g. `impl Foo for &T`
MethodReceiverRefImpl,
Callee,
ImplArg(HirId),
FieldAccess(Symbol),
Postfix,
Deref,
@ -630,7 +659,7 @@ fn precedence(self) -> i8 {
| Self::Callee
| Self::FieldAccess(_)
| Self::Postfix => PREC_POSTFIX,
Self::Deref => PREC_PREFIX,
Self::ImplArg(_) | Self::Deref => PREC_PREFIX,
Self::DerefStable(p, _) | Self::ReborrowStable(p) | Self::Other(p) => p,
}
}
@ -639,8 +668,12 @@ fn precedence(self) -> i8 {
/// Walks up the parent expressions attempting to determine both how stable the auto-deref result
/// is, and which adjustments will be applied to it. Note this will not consider auto-borrow
/// locations as those follow different rules.
#[allow(clippy::too_many_lines)]
fn walk_parents<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> (Position, &'tcx [Adjustment<'tcx>]) {
#[expect(clippy::too_many_lines)]
fn walk_parents<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
msrv: Option<RustcVersion>,
) -> (Position, &'tcx [Adjustment<'tcx>]) {
let mut adjustments = [].as_slice();
let mut precedence = 0i8;
let ctxt = e.span.ctxt();
@ -732,13 +765,20 @@ fn walk_parents<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> (Position, &
.iter()
.position(|arg| arg.hir_id == child_id)
.zip(expr_sig(cx, func))
.and_then(|(i, sig)| sig.input_with_hir(i))
.map(|(hir_ty, ty)| match hir_ty {
.and_then(|(i, sig)| {
sig.input_with_hir(i).map(|(hir_ty, ty)| match hir_ty {
// Type inference for closures can depend on how they're called. Only go by the explicit
// types here.
Some(hir_ty) => binding_ty_auto_deref_stability(cx, hir_ty, precedence, ty.bound_vars()),
None => ty_auto_deref_stability(cx, cx.tcx.erase_late_bound_regions(ty), precedence)
.position_for_arg(),
None => {
if let ty::Param(param_ty) = ty.skip_binder().kind() {
needless_borrow_impl_arg_position(cx, parent, i, *param_ty, e, precedence, msrv)
} else {
ty_auto_deref_stability(cx, cx.tcx.erase_late_bound_regions(ty), precedence)
.position_for_arg()
}
},
})
}),
ExprKind::MethodCall(_, args, _) => {
let id = cx.typeck_results().type_dependent_def_id(parent.hir_id).unwrap();
@ -778,6 +818,10 @@ fn walk_parents<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> (Position, &
} else {
Position::MethodReceiver
}
} else {
let ty = cx.tcx.fn_sig(id).skip_binder().inputs()[i];
if let ty::Param(param_ty) = ty.kind() {
needless_borrow_impl_arg_position(cx, parent, i, *param_ty, e, precedence, msrv)
} else {
ty_auto_deref_stability(
cx,
@ -786,6 +830,7 @@ fn walk_parents<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> (Position, &
)
.position_for_arg()
}
}
})
},
ExprKind::Struct(path, fields, _) => {
@ -946,6 +991,205 @@ fn visit_generic_arg(&mut self, arg: &GenericArg<'_>) {
v.0
}
// Checks whether:
// * child is an expression of the form `&e` in an argument position requiring an `impl Trait`
// * `e`'s type implements `Trait` and is copyable
// If the conditions are met, returns `Some(Position::ImplArg(..))`; otherwise, returns `None`.
// The "is copyable" condition is to avoid the case where removing the `&` means `e` would have to
// be moved, but it cannot be.
fn needless_borrow_impl_arg_position<'tcx>(
cx: &LateContext<'tcx>,
parent: &Expr<'tcx>,
arg_index: usize,
param_ty: ParamTy,
mut expr: &Expr<'tcx>,
precedence: i8,
msrv: Option<RustcVersion>,
) -> Position {
let destruct_trait_def_id = cx.tcx.lang_items().destruct_trait();
let sized_trait_def_id = cx.tcx.lang_items().sized_trait();
let Some(callee_def_id) = fn_def_id(cx, parent) else { return Position::Other(precedence) };
let fn_sig = cx.tcx.fn_sig(callee_def_id).skip_binder();
let substs_with_expr_ty = cx
.typeck_results()
.node_substs(if let ExprKind::Call(callee, _) = parent.kind {
callee.hir_id
} else {
parent.hir_id
});
let predicates = cx.tcx.param_env(callee_def_id).caller_bounds();
let projection_predicates = predicates
.iter()
.filter_map(|predicate| {
if let PredicateKind::Projection(projection_predicate) = predicate.kind().skip_binder() {
Some(projection_predicate)
} else {
None
}
})
.collect::<Vec<_>>();
let mut trait_with_ref_mut_self_method = false;
// If no traits were found, or only the `Destruct`, `Sized`, or `Any` traits were found, return.
if predicates
.iter()
.filter_map(|predicate| {
if let PredicateKind::Trait(trait_predicate) = predicate.kind().skip_binder()
&& trait_predicate.trait_ref.self_ty() == param_ty.to_ty(cx.tcx)
{
Some(trait_predicate.trait_ref.def_id)
} else {
None
}
})
.inspect(|trait_def_id| {
trait_with_ref_mut_self_method |= has_ref_mut_self_method(cx, *trait_def_id);
})
.all(|trait_def_id| {
Some(trait_def_id) == destruct_trait_def_id
|| Some(trait_def_id) == sized_trait_def_id
|| cx.tcx.is_diagnostic_item(sym::Any, trait_def_id)
})
{
return Position::Other(precedence);
}
// `substs_with_referent_ty` can be constructed outside of `check_referent` because the same
// elements are modified each time `check_referent` is called.
let mut substs_with_referent_ty = substs_with_expr_ty.to_vec();
let mut check_referent = |referent| {
let referent_ty = cx.typeck_results().expr_ty(referent);
if !is_copy(cx, referent_ty) {
return false;
}
// https://github.com/rust-lang/rust-clippy/pull/9136#pullrequestreview-1037379321
if trait_with_ref_mut_self_method && !matches!(referent_ty.kind(), ty::Ref(_, _, Mutability::Mut)) {
return false;
}
if !replace_types(
cx,
param_ty,
referent_ty,
fn_sig,
arg_index,
&projection_predicates,
&mut substs_with_referent_ty,
) {
return false;
}
predicates.iter().all(|predicate| {
if let PredicateKind::Trait(trait_predicate) = predicate.kind().skip_binder()
&& cx.tcx.is_diagnostic_item(sym::IntoIterator, trait_predicate.trait_ref.def_id)
&& let ty::Param(param_ty) = trait_predicate.self_ty().kind()
&& let GenericArgKind::Type(ty) = substs_with_referent_ty[param_ty.index as usize].unpack()
&& ty.is_array()
&& !meets_msrv(msrv, msrvs::ARRAY_INTO_ITERATOR)
{
return false;
}
let predicate = EarlyBinder(predicate).subst(cx.tcx, &substs_with_referent_ty);
let obligation = Obligation::new(ObligationCause::dummy(), cx.param_env, predicate);
cx.tcx
.infer_ctxt()
.enter(|infcx| infcx.predicate_must_hold_modulo_regions(&obligation))
})
};
let mut needless_borrow = false;
while let ExprKind::AddrOf(_, _, referent) = expr.kind {
if !check_referent(referent) {
break;
}
expr = referent;
needless_borrow = true;
}
if needless_borrow {
Position::ImplArg(expr.hir_id)
} else {
Position::Other(precedence)
}
}
fn has_ref_mut_self_method(cx: &LateContext<'_>, trait_def_id: DefId) -> bool {
cx.tcx
.associated_items(trait_def_id)
.in_definition_order()
.any(|assoc_item| {
if assoc_item.fn_has_self_parameter {
let self_ty = cx.tcx.fn_sig(assoc_item.def_id).skip_binder().inputs()[0];
matches!(self_ty.kind(), ty::Ref(_, _, Mutability::Mut))
} else {
false
}
})
}
// Iteratively replaces `param_ty` with `new_ty` in `substs`, and similarly for each resulting
// projected type that is a type parameter. Returns `false` if replacing the types would have an
// effect on the function signature beyond substituting `new_ty` for `param_ty`.
// See: https://github.com/rust-lang/rust-clippy/pull/9136#discussion_r927212757
fn replace_types<'tcx>(
cx: &LateContext<'tcx>,
param_ty: ParamTy,
new_ty: Ty<'tcx>,
fn_sig: FnSig<'tcx>,
arg_index: usize,
projection_predicates: &[ProjectionPredicate<'tcx>],
substs: &mut [ty::GenericArg<'tcx>],
) -> bool {
let mut replaced = BitSet::new_empty(substs.len());
let mut deque = VecDeque::with_capacity(substs.len());
deque.push_back((param_ty, new_ty));
while let Some((param_ty, new_ty)) = deque.pop_front() {
// If `replaced.is_empty()`, then `param_ty` and `new_ty` are those initially passed in.
if !fn_sig
.inputs_and_output
.iter()
.enumerate()
.all(|(i, ty)| (replaced.is_empty() && i == arg_index) || !contains_ty(ty, param_ty.to_ty(cx.tcx)))
{
return false;
}
substs[param_ty.index as usize] = ty::GenericArg::from(new_ty);
// The `replaced.insert(...)` check provides some protection against infinite loops.
if replaced.insert(param_ty.index) {
for projection_predicate in projection_predicates {
if projection_predicate.projection_ty.self_ty() == param_ty.to_ty(cx.tcx)
&& let ty::Term::Ty(term_ty) = projection_predicate.term
&& let ty::Param(term_param_ty) = term_ty.kind()
{
let item_def_id = projection_predicate.projection_ty.item_def_id;
let assoc_item = cx.tcx.associated_item(item_def_id);
let projection = cx.tcx
.mk_projection(assoc_item.def_id, cx.tcx.mk_substs_trait(new_ty, &[]));
if let Ok(projected_ty) = cx.tcx.try_normalize_erasing_regions(cx.param_env, projection)
&& substs[term_param_ty.index as usize] != ty::GenericArg::from(projected_ty)
{
deque.push_back((*term_param_ty, projected_ty));
}
}
}
}
}
true
}
struct TyPosition<'tcx> {
position: Position,
ty: Option<Ty<'tcx>>,
@ -1084,7 +1328,8 @@ fn report<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, state: State, data
},
State::DerefedBorrow(state) => {
let mut app = Applicability::MachineApplicable;
let (snip, snip_is_macro) = snippet_with_context(cx, expr.span, data.span.ctxt(), "..", &mut app);
let snip_expr = state.snip_expr.map_or(expr, |hir_id| cx.tcx.hir().expect_expr(hir_id));
let (snip, snip_is_macro) = snippet_with_context(cx, snip_expr.span, data.span.ctxt(), "..", &mut app);
span_lint_hir_and_then(cx, NEEDLESS_BORROW, data.hir_id, data.span, state.msg, |diag| {
let calls_field = matches!(expr.kind, ExprKind::Field(..)) && matches!(data.position, Position::Callee);
let sugg = if !snip_is_macro

2
clippy_lints/src/lib.rs
View File

@ -821,7 +821,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
store.register_late_pass(|| Box::new(verbose_file_reads::VerboseFileReads));
store.register_late_pass(|| Box::new(redundant_pub_crate::RedundantPubCrate::default()));
store.register_late_pass(|| Box::new(unnamed_address::UnnamedAddress));
store.register_late_pass(|| Box::new(dereference::Dereferencing::default()));
store.register_late_pass(move || Box::new(dereference::Dereferencing::new(msrv)));
store.register_late_pass(|| Box::new(option_if_let_else::OptionIfLetElse));
store.register_late_pass(|| Box::new(future_not_send::FutureNotSend));
store.register_late_pass(|| Box::new(if_let_mutex::IfLetMutex));

19
clippy_lints/src/methods/unnecessary_to_owned.rs
View File

@ -6,9 +6,8 @@
contains_ty, get_associated_type, get_iterator_item_ty, implements_trait, is_copy, is_type_diagnostic_item,
peel_mid_ty_refs,
};
use clippy_utils::{meets_msrv, msrvs};
use clippy_utils::{fn_def_id, get_parent_expr, is_diag_item_method, is_diag_trait_item};
use clippy_utils::{meets_msrv, msrvs};
use rustc_errors::Applicability;
use rustc_hir::{def_id::DefId, BorrowKind, Expr, ExprKind};
use rustc_lint::LateContext;
@ -373,25 +372,15 @@ fn get_input_traits_and_projections<'tcx>(
) -> (Vec<TraitPredicate<'tcx>>, Vec<ProjectionPredicate<'tcx>>) {
let mut trait_predicates = Vec::new();
let mut projection_predicates = Vec::new();
for (predicate, _) in cx.tcx.predicates_of(callee_def_id).predicates.iter() {
// `substs` should have 1 + n elements. The first is the type on the left hand side of an
// `as`. The remaining n are trait parameters.
let is_input_substs = |substs: SubstsRef<'tcx>| {
if_chain! {
if let Some(arg) = substs.iter().next();
if let GenericArgKind::Type(arg_ty) = arg.unpack();
if arg_ty == input;
then { true } else { false }
}
};
for predicate in cx.tcx.param_env(callee_def_id).caller_bounds() {
match predicate.kind().skip_binder() {
PredicateKind::Trait(trait_predicate) => {
if is_input_substs(trait_predicate.trait_ref.substs) {
if trait_predicate.trait_ref.self_ty() == input {
trait_predicates.push(trait_predicate);
}
},
PredicateKind::Projection(projection_predicate) => {
if is_input_substs(projection_predicate.projection_ty.substs) {
if projection_predicate.projection_ty.self_ty() == input {
projection_predicates.push(projection_predicate);
}
},

2
clippy_utils/src/msrvs.rs
View File

@ -13,7 +13,7 @@ macro_rules! msrv_aliases {
// names may refer to stabilized feature flags or library items
msrv_aliases! {
1,62,0 { BOOL_THEN_SOME }
1,53,0 { OR_PATTERNS, MANUAL_BITS, BTREE_MAP_RETAIN, BTREE_SET_RETAIN }
1,53,0 { OR_PATTERNS, MANUAL_BITS, BTREE_MAP_RETAIN, BTREE_SET_RETAIN, ARRAY_INTO_ITERATOR }
1,52,0 { STR_SPLIT_ONCE, REM_EUCLID_CONST }
1,51,0 { BORROW_AS_PTR, UNSIGNED_ABS }
1,50,0 { BOOL_THEN }

117
tests/ui/needless_borrow.fixed
View File

@ -1,6 +1,6 @@
// run-rustfix
#![feature(lint_reasons)]
#![feature(custom_inner_attributes, lint_reasons)]
#[warn(clippy::all, clippy::needless_borrow)]
#[allow(unused_variables, clippy::unnecessary_mut_passed)]
@ -127,6 +127,20 @@ fn main() {
0
}
}
let _ = std::process::Command::new("ls").args(["-a", "-l"]).status().unwrap();
let _ = std::path::Path::new(".").join(".");
deref_target_is_x(X);
multiple_constraints([[""]]);
multiple_constraints_normalizes_to_same(X, X);
let _ = Some("").unwrap_or("");
only_sized(&""); // Don't lint. `Sized` is only bound
let _ = std::any::Any::type_id(&""); // Don't lint. `Any` is only bound
let _ = Box::new(&""); // Don't lint. Type parameter appears in return type
ref_as_ref_path(&""); // Don't lint. Argument type is not a type parameter
refs_only(&()); // Don't lint. `&T` implements trait, but `T` doesn't
multiple_constraints_normalizes_to_different(&[[""]], &[""]); // Don't lint. Projected type appears in arguments
}
#[allow(clippy::needless_borrowed_reference)]
@ -183,3 +197,104 @@ mod issue9160 {
}
}
}
#[derive(Clone, Copy)]
struct X;
impl std::ops::Deref for X {
type Target = X;
fn deref(&self) -> &Self::Target {
self
}
}
fn deref_target_is_x<T>(_: T)
where
T: std::ops::Deref<Target = X>,
{
}
fn multiple_constraints<T, U, V, X, Y>(_: T)
where
T: IntoIterator<Item = U> + IntoIterator<Item = X>,
U: IntoIterator<Item = V>,
V: AsRef<str>,
X: IntoIterator<Item = Y>,
Y: AsRef<std::ffi::OsStr>,
{
}
fn multiple_constraints_normalizes_to_same<T, U, V>(_: T, _: V)
where
T: std::ops::Deref<Target = U>,
U: std::ops::Deref<Target = V>,
{
}
fn only_sized<T>(_: T) {}
fn ref_as_ref_path<T: 'static>(_: &'static T)
where
&'static T: AsRef<std::path::Path>,
{
}
trait RefsOnly {
type Referent;
}
impl<T> RefsOnly for &T {
type Referent = T;
}
fn refs_only<T, U>(_: T)
where
T: RefsOnly<Referent = U>,
{
}
fn multiple_constraints_normalizes_to_different<T, U, V>(_: T, _: U)
where
T: IntoIterator<Item = U>,
U: IntoIterator<Item = V>,
V: AsRef<str>,
{
}
// https://github.com/rust-lang/rust-clippy/pull/9136#pullrequestreview-1037379321
#[allow(dead_code)]
mod copyable_iterator {
#[derive(Clone, Copy)]
struct Iter;
impl Iterator for Iter {
type Item = ();
fn next(&mut self) -> Option<Self::Item> {
None
}
}
fn takes_iter(_: impl Iterator) {}
fn dont_warn(mut x: Iter) {
takes_iter(&mut x);
}
fn warn(mut x: &mut Iter) {
takes_iter(&mut x)
}
}
mod under_msrv {
#![allow(dead_code)]
#![clippy::msrv = "1.52.0"]
fn foo() {
let _ = std::process::Command::new("ls").args(&["-a", "-l"]).status().unwrap();
}
}
mod meets_msrv {
#![allow(dead_code)]
#![clippy::msrv = "1.53.0"]
fn foo() {
let _ = std::process::Command::new("ls").args(["-a", "-l"]).status().unwrap();
}
}

117
tests/ui/needless_borrow.rs
View File

@ -1,6 +1,6 @@
// run-rustfix
#![feature(lint_reasons)]
#![feature(custom_inner_attributes, lint_reasons)]
#[warn(clippy::all, clippy::needless_borrow)]
#[allow(unused_variables, clippy::unnecessary_mut_passed)]
@ -127,6 +127,20 @@ fn from(s: &S) -> Self {
0
}
}
let _ = std::process::Command::new("ls").args(&["-a", "-l"]).status().unwrap();
let _ = std::path::Path::new(".").join(&&".");
deref_target_is_x(&X);
multiple_constraints(&[[""]]);
multiple_constraints_normalizes_to_same(&X, X);
let _ = Some("").unwrap_or(&"");
only_sized(&""); // Don't lint. `Sized` is only bound
let _ = std::any::Any::type_id(&""); // Don't lint. `Any` is only bound
let _ = Box::new(&""); // Don't lint. Type parameter appears in return type
ref_as_ref_path(&""); // Don't lint. Argument type is not a type parameter
refs_only(&()); // Don't lint. `&T` implements trait, but `T` doesn't
multiple_constraints_normalizes_to_different(&[[""]], &[""]); // Don't lint. Projected type appears in arguments
}
#[allow(clippy::needless_borrowed_reference)]
@ -183,3 +197,104 @@ fn calls_mut_field(&mut self) -> T {
}
}
}
#[derive(Clone, Copy)]
struct X;
impl std::ops::Deref for X {
type Target = X;
fn deref(&self) -> &Self::Target {
self
}
}
fn deref_target_is_x<T>(_: T)
where
T: std::ops::Deref<Target = X>,
{
}
fn multiple_constraints<T, U, V, X, Y>(_: T)
where
T: IntoIterator<Item = U> + IntoIterator<Item = X>,
U: IntoIterator<Item = V>,
V: AsRef<str>,
X: IntoIterator<Item = Y>,
Y: AsRef<std::ffi::OsStr>,
{
}
fn multiple_constraints_normalizes_to_same<T, U, V>(_: T, _: V)
where
T: std::ops::Deref<Target = U>,
U: std::ops::Deref<Target = V>,
{
}
fn only_sized<T>(_: T) {}
fn ref_as_ref_path<T: 'static>(_: &'static T)
where
&'static T: AsRef<std::path::Path>,
{
}
trait RefsOnly {
type Referent;
}
impl<T> RefsOnly for &T {
type Referent = T;
}
fn refs_only<T, U>(_: T)
where
T: RefsOnly<Referent = U>,
{
}
fn multiple_constraints_normalizes_to_different<T, U, V>(_: T, _: U)
where
T: IntoIterator<Item = U>,
U: IntoIterator<Item = V>,
V: AsRef<str>,
{
}
// https://github.com/rust-lang/rust-clippy/pull/9136#pullrequestreview-1037379321
#[allow(dead_code)]
mod copyable_iterator {
#[derive(Clone, Copy)]
struct Iter;
impl Iterator for Iter {
type Item = ();
fn next(&mut self) -> Option<Self::Item> {
None
}
}
fn takes_iter(_: impl Iterator) {}
fn dont_warn(mut x: Iter) {
takes_iter(&mut x);
}
fn warn(mut x: &mut Iter) {
takes_iter(&mut x)
}
}
mod under_msrv {
#![allow(dead_code)]
#![clippy::msrv = "1.52.0"]
fn foo() {
let _ = std::process::Command::new("ls").args(&["-a", "-l"]).status().unwrap();
}
}
mod meets_msrv {
#![allow(dead_code)]
#![clippy::msrv = "1.53.0"]
fn foo() {
let _ = std::process::Command::new("ls").args(&["-a", "-l"]).status().unwrap();
}
}

48
tests/ui/needless_borrow.stderr
View File

@ -120,17 +120,59 @@ error: this expression creates a reference which is immediately dereferenced by
LL | (&&5).foo();
| ^^^^^ help: change this to: `(&5)`
error: the borrowed expression implements the required traits
--> $DIR/needless_borrow.rs:131:51
|
LL | let _ = std::process::Command::new("ls").args(&["-a", "-l"]).status().unwrap();
| ^^^^^^^^^^^^^ help: change this to: `["-a", "-l"]`
error: the borrowed expression implements the required traits
--> $DIR/needless_borrow.rs:132:44
|
LL | let _ = std::path::Path::new(".").join(&&".");
| ^^^^^ help: change this to: `"."`
error: the borrowed expression implements the required traits
--> $DIR/needless_borrow.rs:133:23
|
LL | deref_target_is_x(&X);
| ^^ help: change this to: `X`
error: the borrowed expression implements the required traits
--> $DIR/needless_borrow.rs:134:26
|
LL | multiple_constraints(&[[""]]);
| ^^^^^^^ help: change this to: `[[""]]`
error: the borrowed expression implements the required traits
--> $DIR/needless_borrow.rs:135:45
|
LL | multiple_constraints_normalizes_to_same(&X, X);
| ^^ help: change this to: `X`
error: this expression creates a reference which is immediately dereferenced by the compiler
--> $DIR/needless_borrow.rs:136:32
|
LL | let _ = Some("").unwrap_or(&"");
| ^^^ help: change this to: `""`
error: this expression borrows a value the compiler would automatically borrow
--> $DIR/needless_borrow.rs:173:13
--> $DIR/needless_borrow.rs:187:13
|
LL | (&self.f)()
| ^^^^^^^^^ help: change this to: `(self.f)`
error: this expression borrows a value the compiler would automatically borrow
--> $DIR/needless_borrow.rs:182:13
--> $DIR/needless_borrow.rs:196:13
|
LL | (&mut self.f)()
| ^^^^^^^^^^^^^ help: change this to: `(self.f)`
error: aborting due to 22 previous errors
error: the borrowed expression implements the required traits
--> $DIR/needless_borrow.rs:298:55
|
LL | let _ = std::process::Command::new("ls").args(&["-a", "-l"]).status().unwrap();
| ^^^^^^^^^^^^^ help: change this to: `["-a", "-l"]`
error: aborting due to 29 previous errors